1. Field of the Invention
The invention relates to an adjusting device for varying the phase angle between an input shaft and an output shaft of an endless chain drive between a sheet feeder and a printing unit of a sheet-fed printing press, wherein the chain drive is formed with a tight side and a slack side and defines an inner space.
Such an adjusting device provides an infinitely variable adjustment of phase between the sheet feeder and the printing unit in order to accommodate them to different operating conditions arising from different press speeds. It is thus possible, in particular, to achieve a phase lead of the sheet in the feeder in order to compensate, at high press speeds, for delays in the arrival of the sheet, so that the leading edge of the sheet will have safely and reliably reached the front lays by the time the transverse alignment has taken place.
2. Description of the Related Art
An adjusting device has become known heretofore from U.S. Pat. No. 4,791,869 wherein a tensioning element acting outwardly from within against the tight side of a chain and against the slack side thereof are disposed on a common slide which, for the purpose of phase adjustment, is displaceable substantially perpendicularly to a plane in which respective axes of the two shafts are disposed. The two tensioning elements, one of which acts from the inside against the tight side of the chain drive and the other of which acts from the inside against the slack side of the chain drive, are pretensioned in the direction of action by a spring.
A comparable device has also become known heretofore from U.S. Pat. No. 1,819,743 wherein the slide for the adjustment is guided on laterally disposed rods, and the adjustment of the slide is accomplished by means of a rotatable spindle having a male thread which engages with a female thread formed in the slide.